Schema:
Problem_Category_Codes (problem_category_code, problem_category_description)
Problem_Log (problem_log_id, assigned_to_staff_id, problem_id, problem_category_code, problem_status_code, log_entry_date, log_entry_description, log_entry_fix, other_log_details)
Problem_Status_Codes (problem_status_code, problem_status_description)
Product (product_id, product_name, product_details)
Staff (staff_id, staff_first_name, staff_last_name, other_staff_details)
Problems (problem_id, product_id, closure_authorised_by_staff_id, reported_by_staff_id, date_problem_reported, date_problem_closed, problem_description, other_problem_details)
Please answer with SQL.